
import math

def run():
    x1,y1,x2,y2=tuple(map(float,input().split()))
    
    r=math.sqrt((x1-x2)**2+(y1-y2)**2)
    
    
    print(f"{r:.30f}")


run() import math math def run():
    x1,y1,x2,y2=tuple(map(float,input().split()))
    
    r=math.sqrt((x1-x2)**2+(y1-y2)**2)
    
    
    print(f"{r:.30f}") run x1,y1,x2,y2=tuple(map(float,input().split())) x1 tuple(map(float,input().split())) tuple map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 r=math.sqrt((x1-x2)**2+(y1-y2)**2) r math.sqrt((x1-x2)**2+(y1-y2)**2) math.sqrt math sqrt (x1-x2)**2+(y1-y2)**2 (x1-x2)**2 x1-x2 x1 x2 2 (y1-y2)**2 y1-y2 y1 y2 2 print(f"{r:.30f}") print f"{r:.30f}" run() run def run():
    x1,y1,x2,y2=tuple(map(float,input().split()))
    
    r=math.sqrt((x1-x2)**2+(y1-y2)**2)
    
    
    print(f"{r:.30f}") def run():
    x1,y1,x2,y2=tuple(map(float,input().split()))
    
    r=math.sqrt((x1-x2)**2+(y1-y2)**2)
    
    
    print(f"{r:.30f}") run

import math

def run():
    x1,y1,x2,y2=tuple(map(float,input().split()))
    
    r=math.sqrt((x1-x2)**2+(y1-y2)**2)
    
    
    print(f"{r:.30f}")


run()
